1. Field of the Invention
The present invention relates to a method of manufacturing a recording medium that improves yields in mass production and shows stable characteristics, and also relates to a recording medium having a novel configuration manufactured by such a method. In particular, the invention relates to a method of manufacturing a recording medium suitable for inkjet-recording. More specifically, the invention relates to: a method of manufacturing a recording medium with improved productivity, which allows a manufacturer to stably produce a recording medium having excellent characteristics in quantity and eventually provides a recording medium with excellent characteristics with respect to ink-absorbency and color development while preventing generation of cracks in an ink-receiving layer of the recording medium; and a recording medium manufactured by such a method.
2. Related Background Art
In late years, for an inkjet-recording system, the size reduction of an ink droplet and the improvement of ink have been extensively advanced since improved recording characteristics of such a system, such as a higher recording speed and a higher definition, have been attained, resulting in further improved image qualities. Therefore, the inkjet-recording system, as being represented by a high-resolution inkjet printer described as a photo printer, is capable of providing a high-quality image, which can be compared favorably with a silver halide photograph. Thus, the number of users who print full-color images taken by digital cameras or the like is increasing now. Furthermore, with respect to a recoding medium on which such image information is to be recorded, a photo-grade glossy recording medium becomes demanded for obtaining an image like a silver halide photograph. For addressing such a demand, it has been conventionally known that a high-glossy recording medium can be obtained by applying a casting method on a recording medium having an ink-receiving layer in which alumina hydrate and polyvinyl alcohol are used as components of a binder. In Particular, in JP 2001-138628 A (Document 1) that attains a gloss for inkjet, there is disclosed an invention in which an ink-receiving layer is re-swelled as a technique for improving the casting method.
Such a formation of the ink-receiving layer using both alumina hydrate and polyvinyl alcohol as components of a binder has been well known in the art. In this case, however, it is important to manage a change with time in thickening of a coating liquid that contains alumina hydrate and polyvinyl alcohol. For recognizing a part of such a change with time, in JP 7-76161 A (Document 2), there are proposed an alumina-sol coating liquid and a resin film on which such a coating liquid is applied. In Document 2, the coating liquid contains alumina hydrate, polyvinyl alcohol, and a predetermined amount of boric acid or borate. In this document, however, it is only focused on the coating liquid directly applied on the resin film, and in addition there is only disclosed one having 23 g/m2 of an ink-receiving layer.
Furthermore, with reference to Document 2, JP 11-291621 A (Document 3) indicates the difficulty in stable coating using such a coating liquid disclosed in Document 2 (both Document 2 and Document 3 have been filed by the same applicant). Document 3 is based on a technical idea that denies improvement of the coating liquid and discloses a pre-coating substrate paper obtained by drying base paper mainly composed of paper after a sizing treatment. In this document, more specifically, disclosed is the invention in which base paper is produced in advance by a dry treatment with 0.5 to 1.5 g/m2 of boric acids and a paper-surface treating agent such as a surface paper strengthning agent or a surface sizing agent using a size press. In the example in Document 3, after preparing the base paper, a coating liquid without containing a crosslinking agent composed of boehmite and polyvinyl alcohol is prepared and is then applied on the base paper. Furthermore, the well-known size press means in general that a sizing agent is slightly applied or immersed in the surface of the base paper and is then dried with a drum drier or the like for improving the waterproof property, surface flatness, print appropriateness, and so on of the base paper.
Whatever the case may be, in each of Documents 2 and 3, the conventional problem of thickening of the coating liquid is recognized. In Document 2, the composition of the coating liquid has been studied to find out means to solve such a problem. In Document 3, on the other hand, the base paper is only provided to find out means to solve such a problem.